Construction of electric batteries, especially industrial batteries, has recently been undergoing substantial changes. Not the least has been the automation of many construction steps, including the automatic placement and sealing of battery covers onto their corresponding jars.
It is a well known fact that the terminal posts, connected integrally or otherwise to the charge plates included within the battery jar, often cause problems in such automated construction efforts. This is because they are not always properly angled or sufficiently aligned to be properly received within the narrow tolerances provided in openings therefor. Since it is important to prevent the leaking of battery acid from between terminal post and cover connections, the components comprising the cover-to-post connection must be accurately formed and aligned in order to be properly sealed. Ideally, cover openings for terminal posts would be formed with a close tolerance relative to terminal post design, on the order of 0.030 inch diametrical clearance. To the extent the cover openings are incorrectly sized or positioned, or the terminal posts were not themselves accurately formed, either as to size or positioning, leakage and production problems could result.
Likewise, it is well known that while the negative terminal posts do not grow or move vertically within the battery, the positive terminal posts do grow and increase in height over the life time of the battery since the positive plates, to which the positive posts are attached, can lengthen as a result of chemical change. Such growth must be accommodated, however, and the present invention creates a post-to-cover connection that seals and accommodates such plate growth while dramatically improving automatic cover installation procedures.
One well known technique of sealing between a cover opening and a terminal post is by using a solid rubber bushing which is forced over the terminal post and into the space between the post and the cover. The capacity to both seal and allow for positive plate growth depends on the dimensional accuracy and resilience of the rubber bushing during the life of the battery. Also, as the positive post pushes up through the rubber bushing, some of the corroded outer surface of the post which has been exposed to acid below the bushing passes up into the bushing where it can continue to corrode and eventually cause leakage of acid. Other examples of sealing systems for use at post-to-cover connections can be found in the following patents.
Rigid terminal post and cover structures are shown in Shannon, U.S. Pat. No. 2,663,758 and Ohya et al, U.S. Pat. No. 4,127,707, both of which show an exterior terminal post molded into a cover. Lead terminal bushings have been molded directly with covers for a number of years, and an example is shown in Hayes, Jr. et al, U.S. Pat. No. 3,957,539.
Other examples of terminal post sealing systems employed following cover installation include Skinner et al, U.S. Pat. No. 1,402,673, Beetem, U.S. Pat. No. 1,960,200 and Chassoux, U.S. Pat. No. 3,578,506. Skinner et al shows a molten sealant that is placed within the opening, in the form of a well and the sealant fills the well about the exterior of the terminal post forming a rigid connection. Beetem discloses a sealing structure wherein the sealant is held within a hollow portion of the terminal post with the sealant being forced out between the terminal post and cover when a terminal bolt is screwed in place within the hollow post. British Pat. No. 1,372,407 is somewhat similar as a sealing resin is injected through a channeled terminal post into a cover sealing well. Reference can also be made to Adderley, U.S. Pat. No. 3,918,993 where softened polypropylene is injected through a hollow terminal post to form a rigid seal between that post and the battery cover.
In Crassoux, a relatively large diameter in the cover is provided and the diameter of the post is less than the minimal diameter of the opening. However, a sealing gasket having an outer diameter substantially equal to the diameter of the cover opening and an internal opening with a diameter substantially equal to the outer diameter of the terminal post. This gasket is wedged between the cover and post structure by means of a bolt assembly which uses threads formed directly on the terminal post itself. In each of these instances, however, the resulting seal is rigid and would not permit growth of the sealed terminal post.
British Pat. No. 418,768 discloses a structure wherein the opening in the cover through which the terminal post extends is provided with a rubber ring or coating and the terminal post as provided with a separate rubber coating. When the terminal post is inserted through the opening, the two rubber surfaces engage and form a seal therebetween.
German Offenlegunsschrift No. 2420879 discloses the concept of employing a pitch or resin packing material within a cover well surrounding the terminal post with the packing serving to provide the seal between the cover and terminal post. While some clearance is shown between the opening into the well area and the post, the tolerance must be small enough to prohibit the packing from leaking into the battery. It is not clear whether the post could move relative to the cover.
The Babusci et al U.S. Pat. Nos. 3,434,883 and 3,490,954 disclose a concept wherein a battery cover is provided with a plurality of openings with a depending sleeve integrally formed therebelow. Terminal posts fit very tightly within that opening and O-rings are provided therebetween to both limit lateral movement and act as a secondary seal. The primary seal is a flexible tube of an acid-resistant material one end of which extends about the exterior of the depending sleeve, the other end being fitted around the terminal post.
In Sharpe et al, U.S. Pat. No. 3,652,340, the cover includes post openings defined by depending sleeves. An adhesive coating is formed directly on the terminal post and a one-piece flexible tube assembly is positioned over the post and sealed to it. The tube includes a depending portion which is not sealed to the post but is turned back upon itself so as to extend outwardly over the depending sleeve through which the terminal post extends. That portion of the flexible tube bent back over the depending sleeve provides the primary seal. The post is spaced from the interior of the sleeve and a plurality of sealing ribs are provided on the flexible tube structure adhered to the post and these ribs provide a secondary seal. Such a sealing arrangement must be formed prior to rather than following cover installation.
Hubbauer et al, U.S. Pat. No. 3,678,178, relates to a battery terminal seal which can withstand high pressures and is comprised of an inner plastic bushing about which a metal sleeve has been formed with the plastic bushing being deflected radially outwardly when axially compressed by a nut at the end of the terminal post.
Salamon et al, U.S. Pat. No. 4,075,368, discloses a multiple component post connection for producing a highly conductive but rigid connection. The terminal post itself is a composite structure formed from an internal tinned copper sleeve on which a lead mantle and a pole bridge have been integrally cast. The lead mantle is in direct contact with and passes through a lead receptacle formed with a synthetic plastic coating on its outer surface. This receptacle in turn fits within a sleeve depending from the cover. The two contacting lead portions are subsequently welded together and produce a rigid lead-to-lead connection and the depending sleeve and the plastic coating on the lead receptacle are ultrasonically welded together to form a liquid-tight seal about the entire post assembly.
Salamon, U.S. Pat. No. 4,212,934, concerns a sliding seal where a plastic mantle is cast directly onto the terminal post. In one embodiment the mantle cast on the terminal post is provided with a plurality of integrally formed, outwardly extending ribs which slide along a cylindrically shaped opening within the battery cover. In the second embodiment a groove has been formed about the mantle and a single O-ring lies in the groove providing the sliding seal between the mantle and the cover structure. In each instance, however, the battery posts and the cover openings must be formed with a high degree of accuracy as the size of the cover opening must be such as will precisely receive the terminal post, the integrally cast mantle structure and the projecting sealing ribs or O-ring.
The teachings do not recognize the problem of imprecisely oriented terminal posts nor how this affects automated battery construction which will allow cover installation to be followed by terminal post sealing. Likewise, there has been no recognition of how to solve the sizing and alignment problems that can result with respect to batteries, battery covers and terminal posts.